Sealer, Yorkshire grit and Hampshire sheen advice, please

[HappyPixie]

Hi folks.
I've obviously lost my way, having spent most of my time in the 'woodturning' section.
I completed a cherry bowl yesterday which I sanded to 320 grit, brushed clean and then applied Chestnut cellulose sanding sealer after I switched the lathe off. I patiently waited the requisite five minutes before smearing a light coat of Yorkshire grit all over. Another short wait and then powered up for a couple of minutes of moving the pad over the surface to allow the grit to break down and abrade further and smoother. Then a couple of wipes with clean cloths while it was still whizzing round. Powered down and then smeared with Hampshire sheen. Another few mins and then powered up and polish off the surface with a few more clean cloths. This is the second bowl I've done this way and both times I've got a VERY smooth surface (lovely) but although there is generally a high gloss on most of the surface, there are patches of mid-sheen (see picture). I'm sure I'm following the instructions and I'm not applying too much pressure when gritting or sheening, so I'm stumped.
Should I apply more than one coat of sealer, grit or sheen?
The first bowl was given a light rub with red Mirlon and then hand buffed with microcrystalline wax. That's OK, but I want to know what I've done wrong in the first place.
Cheers all
Steve

 

[CHJ]

Without seeing the finished piece it's difficult to judge the root cause.

It would appear from the images that you have not removed all the across grain scratches, something Cherry is very good at highlighting, maybe they are an indication of differing surface firmness and absorption in certain areas of the grain.

Did you shake the sanding sealer vigorously before use? it's essential to suspend the fillers adequately.

General impression is that you have abraded away the 'sealed' surface and your paste wax solvents are sinking into the wood rather than dispersing and allowing the forming of a glossy skin.

Regarding the application of higher melting point Microcrystalline wax over a paste wax which may well be blended with lower melting point waxes, although compatible as a mix I personally think this is a waste of time because at best you will get a blend of waxes and little benefit from the higher melting point and better handling characteristics of the MC.

 

[HappyPixie]

Thanks CHJ
Lots to consider.
No I didn't shake the cellulose sealer. Bizarrely, I assumed the gloopiness of it showed that all the good stuff was already in suspension.
I can see how I could have Yorkshire gritted my way through the sealer layer and back to the wood in places. Is a second coat of sealer a sensible precaution in future (after I've shaken it, of course).
As for the MC over other wax, your comments make perfect sense. If I can get the sealer and Yorkshire grit sequence working OK, I'd like to see if I can get the Hampshire sheen to work. I got the impression that it is less glossy than MC but you might know better.
As for MC, I wipe it on and leave it to dry off and then put a 50mm mop on an arbour in a hand power drill to polish off. I'm getting the impression that this practice won't heat the wax enough to make it flow and bind to the project. Is that about right?
I hope all this is useful to other readers.
Cheers
Steve

 

[CHJ]

A second coat of sealer on sound wood should not be necessary or any advantage for that matter, on softer spots in punky wood extra coats may be effective but this is because it is swelling and hardening the soft fibres, little to do with the basic sealer aspect of the product.

A 50mm diameter soft cotton mop needs to be running at something like 2000-2500 rpm. (or even higher) to get similar performance to say a 200 mm mop running at 1200-1500 rpm, which is a reasonable norm. I would not expect to get optimum burnishing or polishing from such a small mop in a hand drill.


Have a read through the leaflets and watch the videos on the Chestnut web site for the basics of using a sealer and burnishing after its use.

 

[Phil Pascoe]

... Bizarrely, I assumed the gloopiness of it showed that all the good stuff was already in suspension ...

I'd think if it is remotely gloopy I'd think it needed thinning. Most turners I know dilute it 50/50.

 

[ED65]

Is a second coat of sealer a sensible precaution in future (after I've shaken it, of course).

I think given how thinly these will go on in a turning environment it can't hurt to try.

I've built up multiple coats of (shellac) sanding sealer in the past numerous times and there's a clear discernible difference to two or more over just the one. The reason I first started to apply more than one is simply because a single coat didn't look like it had done enough, and the lightest sanding confirmed this as it too easily exposed bare wood in some spots, including areas where the wood was more absorbent.

 

[Terry Smart]

Thanks CHJ
Is a second coat of sealer a sensible precaution in future (after I've shaken it, of course).

Nope. It's bad practice and although it won't matter too much in the process you're using here, if you do this under a lacquer then you could be heading for trouble, so don't get into the habit.
Besides which, there should be no need. A good sanding sealer will seal the timber, bind the fibres of the wood together and give you a good foundation for your finishing.
Chas has mentioned the exceptions, but as he says in those cases it's being used as a hardener and not a sealer.
Thanks also to Chas for the mention of our YouTube videos; worth a watch, if only as a cure for insomnia!

 

[Simon_M]

There are patches of mid-sheen (see picture)

In the top photo there is a smear that runs 45 degrees top left to bottom right. It's something that I get when applying too much microcrystalline wax. The instructions say: wait 20 minutes between coats and use sparingly.

I've found it better to apply a wax and wait only a few seconds before polishing most (or at least removing any surplus) off, with the lathe running. A second coat can be lightly buffed and then after about 10 minutes polished up as normal.

When de-nibbing the sanding sealant (just one coat, not diluted), I always use a pad (720g) that has a finer grit than the last grit of sandpaper (400g) to avoid introducing further scratches that might show up in a mirror-like finish after waxing. Using a handful of shavings (always to hand) to burnish the wood seems to be like one additional step that's similar to one extra grit level at no additional cost.

Not the issue here, but I read somewhere that it's important to sand with one even pressure and not be tempted to skip intermediate grits e.g. 120g to 180g to 240g to 400g is better than one coarse 120g and then (just) one fine 400g = not done (properly). There's a tendency to be heavy handed with the coarse grits and then apply almost no pressure with the later ones. Really want to scratch consistently throughout!

 

[woodbloke66]

I've just ordered a tub of Yorkshire Grit to try it out. My current regime is to power sand with the Swedish Kirjes system and a Flexipad sander using Abranet abrasives and as far as I can tell, there's no discernible scratch pattern using 80, 120, 180, 240, 320 and 400g so it's going to be interesting to see if the YG makes any substantial difference - Rob